In silico modelling for predicting the cationic hydrophobicity and cytotoxicity of ionic liquids towards the Leukemia rat cell line, Vibrio fischeri and Scenedesmus vacuolatus based on molecular interaction potentials of ions.

In this study we present prediction models for estimating in silico the cationic hydrophobicity and the cytotoxicity (log [1/EC50]) of ionic liquids (ILs) towards the Leukemia rat cell line (IPC-81), the marine bacterium Vibrio fischeri and the limnic green algae Scenedesmus vacuolatus using linear free energy relationship (LFER) descriptors computed by COSMO calculations. The LFER descriptors used for the prediction model (i.e. excess molar refraction (E), dipolarity/polarizability (S), hydrogen-bonding acidity (A), hydrogen-bonding basicity (B) and McGowan volume (V)) were calculated using sub-descriptors (sig2, sig3, HBD3, HBA4, MR, and volume) derived from COSMO-RS, COSMO and OBPROP. With the combination of two solute descriptors (B, V) of the cation we were able to predict cationic hydrophobicity values (log ko ) with r (2) = 0.987 and standard error (SE) = 0.139 log units. By using the calculated log k o values, we were able to deduce a linear toxicity prediction model. In the second prediction study for the cytotoxicity of ILs, analysis of descriptor sensitivity helped us to determine that the McGowan volume (V) terms of the cation was the most important predictor of cytotoxicity and to simplify prediction models for cytotoxicity of ILs towards the IPC-81 (r (2) of 0.778, SE of 0.450 log units), Vibrio fischeri (r (2) of 0.762, SE of 0.529 log units) and Scenedesmus vacuolatus (r (2) of 0.776, SE of 0.825 log units). The robustness and predictivity of the two models for IPC-81 and Vibrio fischeri were checked by comparing the calculated SE and r (2) (coefficient of determination) values of the test set.

Biological effects of imidazolium ionic liquids with varying chain lengths in acute Vibrio fischeri and WST-1 cell viability assays.

Detailed biological studies of methyl- and some ethylimidazolium ionic liquids in luminescent bacteria as well as in the IPC-81 (leukemia cells) and C6 (glioma cells) rat cell lines are presented. Effective concentrations in these test systems are generally some orders of magnitude lower than effective concentrations [corrected] of the conventional solvents acetone, acetonitrile, methanol, and methyl t-butyl ether. No general influence of the anionic compound in the ionic liquids on toxicity could be found, although they seem to modulate toxicity in some cases. The clear influence of the alkyl chain length on toxicity was quantified by linear regression analysis. Alkyl chain length of the longer alkyl chain was varied from 3 to 10 carbon atoms. Consequences for a design of sustainable alternative solvents are briefly sketched.

Influence of solution composition and column aging on the reduction of nitroaromatic compounds by zero-valent iron.

Granular iron is used in reactive permeable barriers for the reductive treatment of organic and inorganic groundwater contaminants. The technology is well established, however, its long-term performance and the importance of the groundwater composition are not yet well understood. Here, the influence of chloride, nitrate, silicate, and Aldrich humic acid on the reactivity of Master Builder iron was studied under anoxic conditions using small packed columns and 2-nitrotoluene (2-NT) as a model contaminant. After initially complete reduction of 2-NT to 2-aminotoluene (2-AT) in the column, possibly under mass-transfer controlled conditions, the reactivity of the iron was found to decrease substantially. In the presence of chloride, this decrease was slowed while exposure to silicate resulted in a very quick loss of iron reactivity. Nitrate was found to interfere strongly with the effect of chloride. These observations are interpreted in terms of corrosion inhibition/promotion and competition. Our results suggest that reactive barrier performance may be strongly affected by the composition of the treated groundwater.

Multidimensional risk analysis of antifouling biocides.

In order to improve the orientation about the long-term sustainability of the use of the antifouling biocides tributyltin (TBT), copper, Irgarol 1051, Sea-Nine 211 and zinc pyrithione, used for the protection of fouling in sea-going ships, the risks posed to the marine biosphere due to their use are evaluated. The newly presented method of risk analysis uses release rate, spatiotemporal range, bioaccumulation, bioactivity and uncertainty as 5 dimensions of ecotoxicological risk. For each dimension, a scoring procedure is briefly described. The resulting risk profiles of the antifouling biocides show characteristics of the different substances, but also indicate where further information is required. Application of the method is proposed as a decision support in the integrated development of products, informed purchasing and for regulatory purposes.